import java.util.LinkedList;
import java.util.Queue;
import java.util.Stack;

class MyStack {

    Queue<Integer> queue1;
    Queue<Integer> queue2;

    public MyStack() {
       queue1 = new LinkedList<>();
       queue2 = new LinkedList<>();
    }

    public void push(int x) {
        if (!queue1.isEmpty()){
            queue1.offer(x);
        } else if (!queue2.isEmpty()){
            queue2.offer(x);
        } else {
            queue1.offer(x);
        }
    }

    public int pop() {
        if (empty()){
            return -1;
        }
        if (!queue1.isEmpty()){
            int size = queue1.size();
            int tmp=-1;
            for (int i=0;i<size-1;i++){
                tmp=queue1.poll();
                queue2.offer(tmp);
            }
            return queue1.poll();
        } else {
            int size = queue2.size();
            int tmp=-1;
            for (int i=0;i<size-1;i++){
                tmp=queue2.poll();
                queue1.offer(tmp);
            }
            return queue2.poll();
        }
    }

    public int top() {
        if (empty()){
            return -1;
        }
        if (!queue1.isEmpty()){
            int size = queue1.size();
            int tmp=-1;
            for (int i=0;i<size;i++){
                tmp=queue1.poll();
                queue2.offer(tmp);
            }
            return tmp;
        } else {
            int size = queue2.size();
            int tmp=-1;
            for (int i=0;i<size;i++){
                tmp=queue2.poll();
                queue1.offer(tmp);
            }
            return tmp;
        }
    }

    public boolean empty() {
        return queue1.isEmpty()&&queue2.isEmpty();
    }
}

public class Text2 {
}
